Check if object exists in another object

Question

I have an object like this:

var obj = {

 heroes: {
        "1": {
          label: "Spiderman"
        },
        "2": {
          label: "Iron Man"
        },
       }
}

What I want to know it, whether there is an object e.g. 2 in obj.heroes.

I tried this, but it didn't work:

var name = "heroes"; //Will be a for-loop later
try {
        if(name["2"] in obj) 
            console.log("There is an 2nd superhero!");

    } catch(e) {console.log(e);}

..got only errors: "Cannot read property '2' of undefined"

I hope you are able to help me. Thanks

You're trying to access a property named 2 in your name object (which is a string). Remove the property accessor from if(name["2"]) — Codeman
– Codeman, Commented Jul 1, 2014 at 22:52

Gabriele Petrioli · Accepted Answer · 2014-07-01 22:54:54Z

1

Try

   if ("2" in obj[name]){
      console.log("There is an 2nd superhero!");
   }

But if you are trying to identify counts, it might be better if you used arrays

var obj = {
   heroes: [
            {label: "Spiderman"},
            {label: "Iron Man"}
           ]
}

And check with

if (obj[name].length > 1) {
    console.log("There is an 2nd superhero!");
}

answered Jul 1, 2014 at 22:54

Gabriele Petrioli

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2 Comments

Standard Over a year ago

Where exactly is the difference? Perfomance? Good style? Just for upgrading my basic knowledge.

Gabriele Petrioli Over a year ago

if the "2" has intrinsic value then you should keep your original code, if - on the other hand - the 2 is just to signify that it is the second item, then you should use an array. It is the right tool for the job, plus it has properties and methods better suited to iterating/counting/adding/removing.. etc..

jjwon · Accepted Answer · 2014-07-02 21:10:39Z

1

You can do something like:

try {
  console.log(obj.heroes["2"]);
} catch (e) {
  console.log('nope :c');
}

However, it would be better to store heroes as an array:

var obj = {
  heroes: [
    {
      label: 'Spiderman'
    },
    {
      label: 'Ironman'
    }
  ]
};

Using the array makes a little more sense since heroes consists of multiple hero objects.

edited Jul 2, 2014 at 21:10

answered Jul 1, 2014 at 22:54

jjwon

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Comments

user2226755 · Accepted Answer · 2014-07-01 22:57:25Z

0

If 2nd superhero doesn't exist the condition return false.

if(obj.heroes["2"]) 
    console.log("There is an 2nd superhero!");

Or :

var count = 0;
for (var x in obj.heroes) {
    if (obj.heroes.hasOwnProperty(x)) {
       count++;
    }
}
console.log("You see "+ count +" heroes.");

answered Jul 1, 2014 at 22:57

user2226755

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Comments

Catalyst · Accepted Answer · 2014-07-02 11:59:45Z

0

this code will hunt it down for you

var delve = function(object, property, dodge) {
        if (!dodge) dodge = object;
        for (var i in object) {
            if (object[i] === dodge) continue;
            if (typeof(object[i]) == typeof({})) this.delve(object[i], property, dodge)
            if (i == property) console.log(object[i]);
        }
    }
delve(heroes,'2')

answered Jul 2, 2014 at 11:59

Catalyst

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